Labs/Jetpack/FlightDeck/Contribution/PrepareFirefox

Add-ons Builder uses the Builder Helper for testing. By default it allows to test addons build on Production, Staging and Trunk servers. To make it work on any other server one has to modify some settings.

First open about:config address. Then find or create extensions.addonBuilderHelper.trustedOrigins preference. Add your development server there (i.e. 127.0.0.1:8000)